This invention relates to a cell for producing high temperatures and high pressures used for synthetizing cubic crystal boron nitride and diamond or the like.
In the synthesis of cubic crystal boron nitride or diamond, an external heating system as shown in FIG. 1 has been most generally used as a device for indirectly heating the mixture of a raw material and a catalyst. In FIG. 1, reference character "a" denotes a sample chamber in which a mixture of a raw material and a catalyst are placed, and "b" an electrically conductive heater element which has been made of a carbon material in general. Reference character "c" denotes a cylindrical member made of an electrically insulating material such as for example alumina or the like. Reference character "d" represents upper and lower discs of an electrically insulating material, "e" a cylindrical member having electrically and thermally insulating properties made, for example of pyrophillite, and "f" electric contact means.
The mixture within the sample chamber "a" is heated by permitting an electric current to flow through the heater element "b".
In this case, the mixture in the sample chamber "a" is heated indirectly. However, the temperature gradient within the sample chamber "a" is large, and the heater element "b" is directly contacted with the electric contact means "f" with high heat loss therefrom. Further, the electric contact means "f" is heated in vicinity of the outer periphery thereof, and so a gasket in contact with the electric contact means "f" is heated. As a result, the pressure sealing effect of the gasket is reduced, and there has been a tendency that sample spouts under a high temperature and a high pressure. Such a tendency was conspicuous particularly in large device.